1. Field of the Invention
The invention relates to belt-type conveyor systems, and more particularly to conveyor systems which carry bulk materials, such as for carrying crushed stone, gravel, coal and the like.
2. Related Prior Art
In known conveyor systems for carrying bulk materials, upper runs of conveyor belts are supported on conveyor belt idlers, which form a particular troughing angle with the upper run of the belt. Such conveyor systems have a loading or impact zone, where the material to be carried by the belt is loaded onto the belt surface. The force of the loading of the material, at the loading zone, applies a particularly high stress to the belt and to the belt supporting idlers.
Commonly, special idler rolls are used in the loading zone, known as impact rollers, which are specially constructed to absorb the loading impact forces. An impact idler assembly is a heavy duty version of the normal conveyor belt idler, in which the rollers are more resistant to impact loading. The rollers are usually three in number, that is, two side rollers and a bottom roller, mounted for rotation on a common support frame, and the rollers may be formed with a cushioning surface, such as in the form of a stack of discs, to resist impact. The two side rollers are oriented at an upwardly extending angle, relative to the center roller, such that the outer rollers extend upwardly toward the lateral edges of the conveyor belt to define a trough area for retaining the material conveyed by the conveyor belt. Thus, the conventional idler roller assembly consists of a series of three transversely oriented individual rollers mounted or supported in end-to-end relation on a common transverse support or saddle frame, and mounted so that the running surfaces of the rollers define the desired troughing angle.
Impact rollers are, themselves, subject to premature and often unpredictable failures. For example, the idler bearings may fail due to the high loading or due to spill-overs or contamination from the material being carried, or from dust. Several factors are known to contribute to the failure of idler rollers. For example, the length of the rollers required to support the conveyor belt is such that deflection of the shaft supporting the roller can occur with application of a force from the load carried by the conveyor belt, resulting in a torque force at the supporting bearings near the ends of the rollers, increasing the wear forces on the bearings. In addition, deflection of the roller shafts cause distortion of the seals located adjacent the bearings at the ends of the rollers, thereby providing an entry point for debris or dust which subsequently contaminates and increases wear of the bearings.
Additionally, the three roller design for defining the troughing of the conveyor belt imparts a sharp comer at the transition between each of the outer rollers and the center roller. This sharp corner promotes premature belt wear, further reducing the operating life for the conveyor system before repair is required.
Also, in the event that it should become necessary to repair or replace one or more of the idler rollers, this usually requires a lengthy shut down of the conveyor since the rollers are provided with fixed mounting points on a rigid structure, and replacement of a roller typically requires lifting the roller out of a bracket. Thus, removal of a roller for inspection or replacement is a time consuming process resulting in a substantial loss of operating time for the conveying system.
A need exists for an improved impact idler roll system which provides extended roll life and reduces belt wear. Additionally a need exists for an idler roll system which facilitates inspection and replacement of idler rolls and reduces down time for conveyor systems.
The present invention provides an idler roller conveyor system, and more particularly a modular roller construction for use in the impact zone of a conveyor system adapted to handle bulk materials deposited on the top run of a conveyor belt supported by the idler rollers.
The modular roller conveyor system of the present invention comprises an elongated support member extending transversely of a conveyor belt run and supporting a plurality of idler roller modules, each module being a self contained unit supported independently on the support member.
Each roller module comprises a support shaft defining a longitudinal axis of rotation, and a shell supported on the support shaft for rotation about the longitudinal axis. The roller module further includes a frame for supporting the support shaft wherein the frame includes first and second end plates engaging opposing first and second ends of the support shaft, and the first and second plates are rigidly affixed to and extend upwardly from a base portion extending parallel to the longitudinal axis. The base portion includes an attachment structure including a pair of elongated, spaced slots extending upwardly into the base portion substantially between the first and second end plates. The slots are adapted to receive upwardly extending cooperating members, having a profile corresponding to the profile of the slots, which are formed on the support member.
The roller modules are mounted to the support member by sliding the modules onto the upwardly extending cooperating members from a transverse side of the support member. The roller modules are positioned across the support member in end-to-end abutting engagement with each other in such a manner as to permit a degree of endwise movement of the roller modules relative to the support member, as well as a certain degree of vertical movement.
The support member is configured with an upwardly concave shape such that the roller modules define a trough shape for supporting the conveyor belt, with the outer lateral edges at a higher elevation than the central portion of the conveyor belt in order to facilitate retention of material on the conveyor belt.
By providing each roller module with an individual pair of end support plates and supporting base portion, each roller shell is supported completely independently of the other rollers and is therefore less constrained from movement in response to impact loads or other forces exerted by materials on the conveyor belt. In this manner, forces from the material loads are permitted to be distributed across the rollers through the limited movement of the roller modules.
In addition, the modular roller conveyor system is provided with five to seven rollers extending transversely across the width of the conveyor belt. In accordance with this design, a shorter support shaft for the roller shell is required, minimizing deflection of the roller shaft and thereby reducing wear on bearings supporting the roller shell for rotation relative to the shaft. The reduced deflection of roller further permits an improved seal to be used with the present roller module, including a labyrinth seal having a close tolerance of approximately 0.0050 inches gap between inner and outer members of the labyrinth seal to substantially preclude intrusion of debris and/or dust to the bearings.
The rollers are further provided with discs or rings formed of an elastomeric material, such as rubber, positioned around the shells for engagement with the lower surface of the upper run of the conveyor belt. The rings or discs provide a cushioning to impact loads exerted by bulk material being deposited on the conveyor belt in the impact zone. The modular roller conveyor system of the present invention thus provides a three-way cushioning of impact loads on the conveyor belt including cushioning provided by 1) the covering of elastomeric material on the roller shells, 2) the roller support frame providing a force absorbing structure, and 3) the movable connection of the roller modules on the support member facilitating distribution of forces across the modular roller conveyor system.
It is accordingly an important object of this invention to provide an impact idler assembly, for belt type material conveying systems, which may be used in place of conventional three roller impact idler systems.
Another object of the present invention is to provide an impact idler roller system which provides improved roller life and belt wear, and which further facilitates inspection and replacement of rollers while minimizing operating system down time.